I have been a passionate home baker since I was a very small child. Even then, it was obvious to me that bought cakes and biscuits are a poor second best on the taste front. I remember begging my mother to buy a Betty Crocker cake mix because I loved the picture on the packet, only to be disillusioned to find that the reality wasn't a patch on what we could knock up in a few minutes. The taste deficit was explained later when, as an investigative food writer, I discovered that most bought baked goods are not only full of chemical additives, but often pretty old by the time we eat them.

To buy cakes, breads and pastries in supermarkets and convenience stores is to step out of the comforting domestic kitchen and into the food industry's science lab. Here, men in white coats have spent years working out how they can take raw ingredients apart, then put them back together again in a more profitable, and nutritionally impoverished, form. The majority of shop-bought baked products are made using cheap commodity oils or artery-clogging, chemically hardened oils such as soya and palm, the plants for which are likely to have been grown on what was once lush rainforest. That sad, soggy sliced loaf comes with obscure emulsifiers, soya flour, vinegar and enzyme-based crumb softeners derived from animals, fungi, cereals and bacteria. Some of these won't show up in the list of ingredients because they are deemed, conveniently, to be "processing aids".

Few bakery products are quite what they seem. Rarely are they made with freshly shelled eggs; rather, dried egg powders and long-life, pre-shelled mixes are the norm. That lemon drizzle cake in your basket might be made with pre-prepared pasteurised lemon zest and lemon "concentrate" in place of fresh zest and juice. Your croissant may owe its smell not to real butter, but to synthetic butter flavouring.

And as if this armoury of additives weren't offputting enough, the packaging of many baked goods is a disaster in environmental terms. A typical birthday cake comes in a cardboard and plastic sleeve, and sits on a cardboard disc coated with thin metal: difficult, if not impossible, to recycle.

Who needs it? Home baking is, pardon the pun, a piece of cake once you get into it. Fresh, warm, wholesome, and made in minutes - you'd be a fool not to.

· Joanna Blythman is the author of Bad Food Britain: How a Nation Ruined Its Appetite (4th Estate)

Typical ingredients

Home-baked

Butter

Sugar

Freshly shelled eggs

Wheat flour: self-raising, or plain with baking powder (bicarbonate of soda and cream of tartar)